1. Field of the Invention
This invention relates to a method of manufacturing heat exchanger tubes (for example, a radiator, a condenser or an evaporator for an automobile) from a plate material payed out continuously, and a dimpling roll used for the same manufacturing method.
2. Description of the Prior Art
A heat exchanger tube enables the heat on the inside and outside thereof to be exchanged with each other by a heating medium circulated inside thereof as the outflow of the heating medium to the outside of the heat exchanger tube is prevented, and cools an apparatus or an engine or sets the temperatures thereof constant. A heat exchanger tube is used for a radiator, a condenser or an evaporator of an automobile. To manufacture this heat exchanger tube, a method of, for example, Japanese Patent Laid-Open No. 028438/1992 is used.
The manufacturing method of Japanese Patent Laid-Open No. 028438/1992 is as follows. This method comprises a plate material dimple-molding step, a cutting step and a bending step, and, during the cutting step, some groups of dimples in a dimple-molded portion are removed, whereby the dimple-removed portions are formed into flat remolded portions corresponding to end portions to be cut of the plate material. A portion corresponding to an end portion to be cut is remolded into a flat portion so as to improve the sealability thereof as an end portion of a heat exchanger tube inserted into an insertion port of a heat exchanger and soldered thereto. According to the techniques which had been utilized before Japanese Patent Laid-Open No. 028438/1992 was published, dimples had also been molded in a cut end portion, so that the sealability of the same end portion soldered to a heat exchanger body had been low.
The invention disclosed in this Japanese Patent Laid-Open No. 028438/1992 can provide a heat exchanger tube capable of easily improving the sealability thereof with respect to a heat exchanger tube. However, since a tube body is formed by bending a plate material after the plate material is cut off, a bending process demands a high accuracy, and a bending operation is difficult to be carried out. This causes a fear of making a cut end portion deviate from an. insertion port of a heat exchanger body, and exerting a bad influence upon a cut end portion inserting operation. Moreover, the elongation, which occurs because cut plate materials flow on a production line, of the cut plate materials in the direction in which a raw plate material is payed out, and a scatter of the dimensional accuracy of cut end portions cannot be ignored. A heat exchanger tube usually demands a dimensional accuracy of xc2x10.2 mm. Therefore, the elongation of a plate material causes the dimensional accuracy of heat exchanger tubes to scatter. Under the circumstances, a heat exchanger tube manufacturing method has been including which is capable of solving these problems, and manufacturing a heat exchanger tube with a high accuracy as the sealability thereof as a heat exchanger tube inserted into a heat exchanger body is maintained.
The present invention relates to a heat exchanger tube manufacturing method for a production line, including a dimpling step of molding a plurality of dimples in a plate material, which is payed out continuously, so as to form the plate material into a molded plate material, a tube body manufacturing step of folding back the molded plate material around an axis extending in the direction in which the plate material is payed out, so as to form the molded plate material into an intermediate tube body, and a step of cutting this intermediate tube body into parts of a predetermined length, the dimpling step including providing the plate material with non-molded sections, in which the dimples are not molded, at predetermined intervals, the cutting step including cutting predetermined parts to be cut of the non-molded sections. The cutting step also includes forming recesses in cut end portions of heat exchanger tubes. The portions to be cut and the portions in which the recesses are to be formed of the intermediate tube body continuously fed are set on and provided in the non-molded sections thereof. To set and provide such portions, reference marks are provided in predetermined positions on the non-molded sections for the purpose of improving the processing accuracy.
According to the present invention, an intermediate tube body obtained by bending a plate material is cut first, so that the problems concerning the processing accuracy are solved. Namely, since the portion of a predetermined range of the plate material which extends from a cut end thereof to a certain extent is formed as a non-molded section, a remolding operation is not required, and both the processing accuracy and sealability of a tube end portion can be set to proper levels. Moreover, the non-molded sections absorb the elongation of the intermediate tube bodies flowing on a production line, and minimize a scatter of the dimensional accuracy of the cut ends. Since the portions to be cut are set additionally on the non-molded sections, the intervals of cut ends can be set certainly in agreement with the length of heat exchanger tubes. The non-molded sections are formed on a plate material by a dimpling roll which constitutes a processing unit used in a dimpling step when heat exchanger tubes are manufactured from a plate material continuously payed out, and which comprises a pair of toothed rolls having toothless non-molded surfaces the rolling cycles of which agree with each other.